simple_paleobathymetry: a config-driven workflow for reconstructing the paleobathymetry of ocean crust

First release of simple_paleobathymetry, a config-driven workflow that reconstructs the paleobathymetry of ocean crust from a plate model and seafloor-age grids. For each time step it converts seafloor age to basement depth (GDH1, Parsons and Sclater, Crosby et al. or RHCW18 age–depth models), computes distances to passive continental margins from the shipped COB line segments or by continent contouring, predicts sediment thickness following Dutkiewicz et al. (2017) and applies an isostatic sediment-load correction, writing one global grid per time. An optional fifth step merges the grids with pyBacktrack paleobathymetry to cover submerged continental crust. Requires predicting-sediment-thickness at commit ec0a867 (see README).